That's because Ganondorf and Link don't always have to space absolutely perfectly to land hits, and Ganondorf at least can punish the mistakes of aggressive players pretty hard.
With Jigglypuff, you always have to be fully mentally alert, because apart from pound, you generally can't challenge your opponents aerials. You have to bait them and weave around them. Jigglypuff places a really high demand on your spacing, just like Link places a high demand on DIing knockback upward, and Ganondorf places a high demand on pwershielding.